Electrochemical cell devices are typically made up of a plurality of electrochemical cells, arranged in groups or stacks, and commonly serve to: electrolytically disassociate water or another liquid (with or without dissolved constituents) into its components (i.e., electrolysis cells), or catalytically combine hydrogen or other fuel and an oxidizer (i.e., fuel cells), with electricity being either supplied or generated, respectively. Other related functions for electrochemical cell devices include their use as compressors, separation and/or purification means, sensors, and combinations of these functions.
Within arranged groups or stacks, each electrochemical cell includes a cathode, an electrolyte (e.g., a membrane), and an anode. In Proton Exchange Membrane or PEM cells, where the electrolyte is a cation exchange membrane, the cathode/membrane/anode assembly (i.e., “membrane electrode assembly” or “MEA”) is typically supported on both sides by flow fields made up of screen packs or channeled plates. Flow fields, usually in the form of expanded metal or woven screens, or adhesive-bonded, laminated, or machined assemblies, facilitate fluid movement, removal of product water or product gas, and also serve to provide in, for example, PEM cells, mechanical support for the MEA.
Electrochemical cells, when operated as fuel cells or water electrolyzers, are desirable for various applications. Fuel cells, for example, have been proposed for many applications including as an energy source for supplying an aircraft with electric energy.
In specific regard to fuel cells with in-cell static water removal capabilities, such cells utilize conductive metal or metallic porous media that functions to remove fuel cell product water via a pressure differential. Unfortunately, this approach, which attempts to balance bubble point with acceptable water transport rates, is usually limited to low, approximately 0.01-0.06 Megapascals (MPa), bubble pressure.
Bubble point is used as a measure of the resistance of the flow of gas phase fluids through pores of filter or filter-like materials. The bubble point value is determined by observing when bubbles first begin to emerge on the permeate side or downstream side of a fully-wetted membrane filter or filter-like material when pressurized with a gas on the feed (upstream) side of the material.
High bubble point materials with excellent water transport exist and are commercially available but when compared to metal or metallic porous media are typically less electrically conductive or non-conductive.
In view of the above, what is needed is a fuel cell that utilizes high bubble point polymeric porous media with excellent water transport capability that has the ability to conduct electrical current.
Generally speaking, the present invention fulfills this need by providing an electrochemical cell that comprises a water/gas porous separator prepared from a polymeric material, and one or more conductive cell components that pass through, or are located in close proximity to, the water/gas porous separator, the electrochemical cell providing a high level of in-cell electrical conductivity.
In an exemplary embodiment, the inventive electrochemical cell operates as an in-cell static water removal fuel cell, wherein the water/gas porous separator is prepared from a high bubble point polymeric material.
The water/gas porous separator employed in this exemplary embodiment has a bubble point of greater than 0.06 MPa, preferably, from about 0.07 to about 0.55 MPa, which provides excellent water removal.
The inventive fuel cell demonstrates an area specific resistance (ASTM # B193-02 (2008) Standard Test Method for Resistivity of Electrical Conductor Materials) of less than or equal to about 100 mohms-cm2, preferably less than about 20 mohm-cm2.
Other features and advantages of the invention will be apparent to one of ordinary skill from the following detailed description and accompanying drawings. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.